Following [1]}, we consider out-of-sample predictive accuracy of the model as our utility function for meta-parameter selection. Our criterion is the Expected Log Pointwise Predictive Density (ELPD),
\(ELPD_{y,z}(Y,Z;\delta ) = \int p^*(y, z) \log {\tilde{p}}^{(k)}_{y,z,\delta }(y, z \mid Y, Z) dy dz,\) 
